Flat tube heat exchanger with more than two flows and a deflecting bottom for motor vehicles, and process for manufacturing the same

ABSTRACT

The invention relates to a flat tube heat exchanger with two or more flows for motor vehicles with a deflecting (or reversing) bottom for deflecting (or reversing) adjacent flows of the flat tubes. According to the invention, it is provided that the deflecting bottom is resolved into deflecting bowls individually assigned to each flat tube, which bowls are connected to one another only via their connection to the respectively assigned flat tubes. The invention also relates to a process for manufacturing such a flat tube beat exchanger by pulling off, straightening and cutting into sections the flat tubes from a coil, mechanically pre-assembling the flat tube heat exchanger from its structural parts including the flat tubes and soldering or brazing. Here, it is provided that the deflecting bowls are mechanically pre-assembled with the flat tubes after they have been cut into sections and before pre-assembling the flat tube heat exchanger with the flat tubes.

BACKGROUND OF THE INVENTION

The invention relates to a flat tube heat exchanger with more than twoflows, preferably an evaporator, for motor vehicles having a deflecting(or reversing) bottom for deflecting (or reversing) adjacent flows ofthe flat tubes with the features of the preamble of claim 1. Such a flattube heat exchanger with a deflecting bottom is known from the DE 195 15528A1. In such flat tube heat exchangers, in the past either deflectingbottoms being an integral part from the beginning or, according to theprior art from which the invention departs, individual deflectingbottoms linked to one another and forming a structural unit as a wholehave been used. In the past, this structure has been provided forstability reasons, and at the other ends of the flat tubes normally acohesion is furthermore effected via the header common to the flattubes, such that this header and the coherent deflecting bottom togetherform a frame-like mounting for the whole structure of the flat tube heatexchanger. This is in particular true for the pre-assembly beforesoldering or brazing, e.g. for preventing the zig zag fins from slippingout before being soldered or brazed.

The term header is generally not to only mean an intermediate header ora header on the outlet side, but also a distributor on the inlet side.

BRIEF SUMMARY OF THE INVENTION

The object underlying the invention is to further simplify the designand the manufacturing process of a flat tube heat exchanger of thementioned type having more than two flows.

This object is solved in a flat tube heat exchanger having more than twoflows with the features of the preamble of claim 1 by the characterizingfeatures thereof.

Equally to the double-flow flat tube heat exchanger according to theDE-A1-195 36 117, in particular FIG. 5, the invention is a renunciationof the idea to effect the respective deflection in an integrallycoherent deflecting bottom. Instead, deep-drawn equal deflecting bowlswhich can be premanufactured are also used as in this known double-flowflat tube heat exchanger.

In the flat tube heat exchangers having more than two flows, to whichthe invention is related, within the deflecting bowl a separation has tobe effected for those adjacent flows which are not deflected to oneanother directly within the respective deflecting bowl. Within the scopeof the invention—and in the preferred further development according toclaim 6—in a novel manner, a necessary separating web is integrallyfinished in the deflecting bowl as a local wall design of the deflectingbowl, which can additionally be effected during deep-drawing thedeflecting bowl and which renders dispensable the requirement toseparately and tightly insert such a separating web or several thereof.

The individual deflecting bowls can be especially easily included in thepre-assembly when manufacturing the flat tube heat exchanger, inparticular according to the manufacturing process of claim 10, and theycan be finished with a greater depth as deflecting compartments ofintegral deflecting bottoms with at least one separating web alreadyshaped therein at equal partition distances. Moreover, their use isespecially favourable if the relative distances between the flat tubesbecome gradually smaller looked from the point of view of a design ofthe flat tube heat exchanger which is as compact as possible. Ingeneral, the invention preferably relates to flat tube heat exchangersmade of aluminum or an aluminum alloy. Correspondingly, the deflectingbowls are also made of aluminum or an aluminum alloy. In this case, theflat tube heat exchanger itself should consist of a material which isalso during soldering compatible with the material of the deflectingbowls, if possible.

A first alternative, preferred due to the easiness of the manufacture,is the local wall design tightly cooperates only with a parting wall ofthe adjacent ducts of the respective flat tube, wherein in a preferredmanner the complete function of the respective flat tube is maintained.However, an equally useful second alternative is possible, i.e. to havethe parting wall between adjacent ducts of related to flows,communicating not directly in the bottom, is formed by a duct of theflat tube which is cut out, i.e. not used or ineffective as a guidingduct for a flow. Apart from the concrete further developments ofreinforcing the wall thickness of the cut out (or ineffective) duct byan inset insertion member that may be sealingly contacted by theseparating web, the use of a cut out duct can be carried out especiallyeasily and advantageously by pressing the separating web in thedeflecting bowl into the duct to be cut out with respect to flows,blocking it at the same time and thus obtaining a seal at the end ofthis duct due to material displacement.

The further development of the invention where the deflecting bowl isdesigned at the inner faces of its two narrow sides with a stop baseeach for the free ends of the front sides of the respective flat tubefavors the assembly as well as the stability of the flat tube. In thisdevelopment, the separating web furthermore has a supplementing centralstop function. In applications of fluxing agents from the outside, thedeflecting bowl is designed at the inner face of its two longitudinalsides, locally in the region of the separating web, with a supply fluteof a fluxing agent for a braze. This favors a secure soldering orbrazing of the deflecting bowl with the flat tube in the especiallycritical region of the separating web.

With deep-drawn parts, such as the deflecting bowls designed with atleast one partition, there is always the problem of evenly designing theedge, as in general, an uneven design results from the deep-drawingprocess. This requires a trimming of this edge. The most simple way torealize this trimming is that the surrounding free edge of thedeflecting bowl is bent to the outside forming an opening in thecarrying out the trimming process in the same direction as thedeep-drawing process. Apart from this, in this inconventional techniqueof the opening up in the form of a tulip, furthermore accidentally aconvenient introducing inclination for the flat tube, not contained inthe deflecting bowls according to FIG. 5 of the DE-A1-195 36 117, or acorresponding introduction radius as an assembly aid is obtained.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be further illustrated by means of schematic drawingsand several embodiments as follows, wherein:

FIG. 1 shows a perspective view of a four-flow flat tube heat exchanger,the flows of which are indicated by arrows;

FIG. 2 shows a sheet metal blank before deep-drawing it to form adeflecting (or reversing) bowl;

FIG. 3 with FIG. 3a show a longitudinal section and a cross-section ofthe connection region of a deflecting (or reversing) bowl to a flattube;

FIG. 3b shows a modification of FIG. 3;

FIG. 4 shows a cross-section through the separating region of thedeflecting (or reversing) bowl according to FIG. 3a; and

FIG. 5, FIG. 5a and FIG. 6 show representations of the kind ofconnection of the deflecting (or reversing) bowl, wherein FIGS. 5 and 5aeach show a section in the connection region to a flat side of the flattube crosswise (FIG. 5) and longitudinal (FIG. 5a) of the flat tube andFIG. 6 shows a partial section in the region of the narrow front side ofthe flat tube longitudinal of the deflecting bowl.

DETAILED DESCRIPTION OF DRAWINGS

The flat tube heat exchanger represented in the figures has a four-flowdesign and is designed as an evaporator of a refrigerant circulation.

This does not exclude the adaption of the represented features to flattube heat exchangers having more than two flows with a different numberof flows, optionally also to those flat tube heat exchangers not servingas an evaporator.

The flat tube heat exchanger has the following general design:

A major number of, typically twenty to thirty, flat tubes 2 is arrangedat constant distances to each other and with aligned front sides 4.Between the flat sides 6 of the flat tubes each, a zig zag fin 8 isinterested in a sandwiched fashion. A zig zag fin 8 each is furthermorearranged at the two outer surfaces of the outer flat tubes. Each flattube comprises internal reinforcing webs 10, which divide off chambers12 into ducts. Depending on the structural depth, a number of thechambers or ducts 12 of ten to thirty is typical.

The mentioned typical regions of the number of flat tubes and thechambers thereof are here only intended to be preferred and not to berestricting.

In a motor vehicle air conditioning equipment, in the final state outerair as an external heat exchange medium flows in the direction of thestructural depth through the block arrangement of the flat tubes 2 andthe zig zag fins 8.

In the evaporator, a refrigerant, such as in particularfluorohydrocarbon, serves as internal heat exchange medium which entersthe flat tube heat exchanger via a supply line 14 and exits the heatexchanger via an outlet line 16. In the refrigerant circulation, thesupply line comes from the liquefier thereof. The outlet line 16 leadsto the condensor of the refrigerant circulation.

In an evaporator, the distribution of the refrigerant on the inlet sideis effected from the supply line 14 to the individual flat tubes by aso-called distributor. On the outlet side, the refrigerant is suppliedas a whole to the outlet line 16. Though it is possible to assign thedistribution and the collection to separate boxes, in all embodimentsboth functions are combined in a common header 18.

This header 18 is then arranged at a front side 4 of the flat tubes 2,while at the other front side 4 of the flat tubes 2, a flow reversetakes place only between each of the flows, here for example by thedeflecting (or reversing) bowls 20 individually assigned to each flattube 2, which can possibly be integrated by links (not shown) to form amodular unit, if necessary.

In the borderline case of a one-flow heat exchanger, the deflectingbowls 20 would be able to take over the function of the connections ofan outlet header, if a common outlet line is connected thereto.

The number of more than two flows means at least a double flow reversein the region of the individual ducts formed by the chambers 12 in eachflat tube 2. Different from the double-flow design, in which thedeflecting bowl 20 would not need any further intermediate chambersubdivision as in its function as a connection of an outlet header, butonly the one-time deflecting function would have to be guaranteed, incase of a deflection of more than two flows, at least the parting wall24 represented in case of a four-flow is necessary, so that in this caseof the four-flow design, a double simple deflection in the respectivedeflecting bowl 20 is effected. In a design with an even greater numberof flows, the number of parting walls 24 optionally is increased.

In the represented embodiments, the header 18 is—without restricting thegenerality—basically composed of a tube bottom 26 and a cap 28, whereinoptionally further parts for assembling the header 18 can be providedwhich are at least partially mentioned in the following.

The free ends of the flat tubes 2 opposite the deflecting bowls 20tightly engage the tube bottom 26 in communication with the inner spaceof the header 18, which tube bottom is correspondingly provided withengaging slits as well as optionally with internal and/or externalengaging muffs.

As in the header 18, the inlet function and the outlet function of therefrigerant are combined, the header 18 requires at least a two-chamberdesign which separates an inlet side from the outlet side. For thispurpose, a chamber subdivision comprises at least one flat web in formof a longitudinal web, which separates the inlet region in the header 18communicating with the supply line 14 from an outlet chamber 34continuously extending longitudinally of the header 18 and communicatingwith the outlet line 16.

In the evaporator, furthermore the supply of the refrigerant on the sideof the inlet to all flat tubes 2 has to be as uniform as possible. In aborderline case, the refrigerant can be supplied to each individual flattube 2 by a so-called distributor. In most cases, however, the supply iseffected to adjacent groups of flat tubes, in which at least some groupscomprise a number of flat tubes higher than one, wherein the number offlat tubes per group can also vary. An own inlet chamber is assigned toeach group of flat tubes, which chamber directly communicates with therespective group of the flat tubes. The inlet chambers are divided offfrom one another in the chamber subdivision by crosswise webs designedas flat webs.

In the represented four-flow evaporator, apart from the longitudinal webwhich divides off the outlet chamber continuous extending longitudinallyof the header 18 and following the outlet line 16, another longitudinalweb in parallel to this web is provided. This web is intersected at aright angle by the crosswise webs divisioning off the own inlet chambersup to a connection to the longitudinal web. In the elongation of thecrosswise webs between the two longitudinal webs, between each of theselongitudinal webs an inner deflection (or reversion) chamber contiguousto the respective outer own inlet chamber for deflecting (reversing) thesecond flow into the third flow is divided off within the header 18.

In case of greater numbers of flows which are guided through the header18 with a deflection (or reversion) function, the number of the furtherlongitudinal webs as well as the number of the inner deflection chambersincrease correspondingly, the deflection chambers then being furthermoreinternested in the crosswise direction of the header situated internallyand one next to the other between the own inlet chambers of the groupsof flat tubes 2 as well as the outlet chamber.

The supply line 14 communicates with each of the individual inletchambers of the groups of flat tubes via an own supply line extending inthe header 18, the design of which can vary and which can be combined inone tube, which can be lead out of the narrow front side of the header18, in this case of the cap 28, together with the bent outer tubeconnection of the supply line 14 to the block valve 50, which will belater discussed, wherein the distribution of the supplied refrigerant tothe own supply lines to the own inlet chambers of the groups of flattubes 2 can be effected directly behind the block valve 50 and beforethe beginning of the bent of the supply line 14.

In most cases, in the assembled heat exchanger the block of flat tubes 2and zig zag fins 8 is laterally terminated by a side sheet metal 46 incontact with each of the outer zig zag fins, such that the side sheetmetals 48 form an outer frame for the outer air flowing against the heatexchanger block according to arrow 6 in FIG. 1.

The flat tubes 2, the zig zag fins 8, the tube bottom 26 and the cap 28of the header together with the optionally provided chamber subdivisionas well as the side sheet metals 46 of the heat exchanger consist, aswell as conveniently the supply line 14 and the outlet line 16, ofaluminum and/or an aluminum alloy and are brazed including the sectionsof the line connections adjacent to the flat tube heat exchanger to formthe finished evaporator, wherein it is possible that the tube bottom 26and the cap 28 are shaped of solder- or braze-coated sheet metal.

Without the invention being restricted thereto, in practice at least inrefrigerant evaporators for motor vehicle air conditioning equipmentaccording to FIG. 1, the supply line 14 and the outlet line 16, whichcan pass over into the header 18 via corresponding connecting sleeves,are connected to two respective connecting sleeves 48 of athermostatically controlled block valve 50. At the opposite side, whichis not shown, this valve comprises two further connecting sleeves at theside of the inlet and of the outlet.

The individual deflecting bowl 20 comprises a bowl bottom 62 which isessentially flat in the shown embodiments, from which rises asurrounding bowl wall with wall sections 66 at the front side andlongitudinal wall sections 68. The flat extension of the bowl bottom 62is here only to be understood as an example. The longitudinal wallsection 68 rises from the bowl bottom 62 essentially at a right angle,such that it overgrips the two flat sides 6 of the respective pertainingflat tube thereby forming a soldering gap. As one can furthermoreparticularly clearly see in FIG. 3, the wall section 66 on the frontside also forms an upright collar 70, which overgrips the narrow frontside 4 of the flat tube also forming a soldering gap, wherein a singlesoldering gap all around the flat tube is formed in the sections on thefront side as well as in the longitudinal sections.

Starting from the low end of the upright collar 70, this collar, whichis only slightly wider than the flat tube 2, respectively passes overinto the flat bowl bottom 62 via a rounded or, according to the drawnrepresentation, straight ramp surface 72, e.g. provided with aninclination angle of about 45°. Here, the two ramp surfaces 72 on thefront side are situated opposite the ducts 12 of the flat tube which arethe front, e.g. three, and last, e.g. two, ducts, seen in the flowdirection of the deflection flow in the deflecting bowl.

The deflecting bowl is deep-drawn from a sheet metal of aluminum or analuminum alloy, which is advantageously coated with braze at the surfaceforming the later inner face of the deflecting bowl. For each deflectingbowl 20, in this case according to FIG. 2 a sheet metal cut out 20 ispunched out of the still flat sheet metal with a pitch (or pitch length)T being greater than the pitch of the arrangement of the flat tubes 2 inthe flat tube heat exchanger, and this cut out is deepdrawn using astamp 3 having the contours of a flat tube 2, the edge sections 66 and68 of the sheet metal cut out 20 being shaped to form the front andlongitudinal wall sections 66 and 68 of the deflecting bowl 20.

In the shown deflecting bowls 20 for the four-flow flat tube heatexchanger, every deflecting bowl forms two deflecting chambers 74 whichare each separated from one another by the parting wall 24 in thedeflecting bowl. The first deflecting chamber 74, seen in the flowdirection of the flows through the respective flat tube 2, deflects (orreverses) the first flow into the second flow, while the otherdeflecting chamber 74 deflects (or reverses) the third flow into thefourth flow. With a higher number of flows, then at least two partingwalls 24 are provided in the deflecting bowl 20 in a manner not shown.

In the embodiments, three types of mounting the parting wall 24 arerepresented.

FIG. 3 describes the general teaching to design the parting wall 24 asintegral part of the deflecting bowl 20 at this bowl itself. FIGS. 3aand 4 describe in this case a type of an integral embodiment of theparting wall 24 which in particular is possible in the manufacture ofthe deflecting bowl from a deep-drawn sheet metal in the sense of FIG.2. Here, the respective longitudinal wall section 68 is each deformed toform an internal crimp 84 extending at a right angle to the bowl bottom62 or extending vertically, respectively. The two similar internalcrimps 84 are in contact at their apexes 68 for forming the closedparting wall 24 or a corresponding separating web between the chambers74, respectively.

Various embodiments furthermore embody various types of connecting therespective parting wall 24 of the deflecting bowl 20 to the flat tube 2.

In the embodiment of FIG. 3, the corresponding parting wall 24 at thefront side 4 of the flat tube 2 is facing each a single reinforcing web10 a of the flat tube 2 in a sealed contact, which separates the secondflow from the third flow in the represented four-flow flat tube heatexchanger. Here, the reinforcing web 10 a can be either offset from thebeginning by having refinished the corresponding front side 4 of theflat tube 2 in preparation of the connection before connecting theparting wall 24, or one can take advantage of the parting wall 24 fordeforming the reinforcing web 10 a when joining the parts. Apart from anot shown blunt connection of the parting wall 24 to the reinforcing web10 a, in particular according to FIG. 3 a connection via a roundedlyprofiled front side of the parting wall 24 is possible. It isappreciated that all mentioned types of connection in all embodiments inwhich a single separating web 10 a in the flat tube 2 cooperates with aparting wall 24 in the deflecting bowl 20 are interchangeable.

A modification of the connection of the parting wall 24 of a deflectingbowl 20 to the flat tube 2 is shown in FIG. 3b. Here, in the connectionregion of the parting wall, a complete duct 12 a of the flat tube 2 iscut out, i.e. not used or ineffective as a guiding duct for a flow. Theparting wall 24 of the deflecting bowl 20 here tightly cooperates withan insertion member 86, which pin-like engages the cut out duct 12 athereby filling out the clear cross-section thereof. Here, the insertionmember 86 has a head part 85 directly cooperating with the parting wall24, which at the back side also overgrips the reinforcing webs 10boundering on both sides the cut out duct 12 a and tightly supportsitself at the reinforcing webs 10 boundering the cut out duct 12 athereby reinforcing the structure of the cut out duct 12 a.

The connection of the deflecting bowl 20 to its related flat tube 2 isfinally illustrated with the preferred connection possibilitiesaccording to FIGS. 5 to 5 a and 6.

According to FIG. 6, in the connection region on the front side at thetransition from the upright collar 70 to the ramp surface 72, a stopbase 87 each for the free ends of the respective flat tube 2 on thefront side is designed.

Generally speaking, the respective deflecting bowl 20 including itsparting wall 24 acting as separating web is soldered with the flat tube2 as well as with the whole flat tube heat exchanger by brazing.

Particular difficulties arise when feeding the fluxing agent for thebrazing in the region where the parting wall 24 is to be soldered to theflat tube 2. This is illustrated in FIGS. 5 and 5a for the particularcase that the parting wall 24 not shown in these figures is to besoldered to a single reinforcing web 10 a of the flat tube. When cuttingout a complete duct 12 a in the sense of FIG. 3b, the arrangement wouldbe correspondingly.

According to FIGS. 5 and 5a, the deflecting bowl 20 comprises at theinternal face 88 of its two longitudinal wall sections 68 locally onboth sides of the reinforcing web 10 a—or in this sense on both sides ofa cut out duct 12 a—each a left open or drawn-in supply flute 89 forsupplying fluxing agents for brazing with the separating web of theparting wall 24. Such pairs of feeding flutes 89 are designed in the twolongitudinal wall sections 68 of the surrounding bowl wall 64 of thedeflecting bowl. At the respective free end of the deflecting bowl 20,they run into a funnel-like outer opening in the form of a tulip 90 ofthis edge provided at that location and extend according to FIG. 5somewhat beyond the free end 4 of the flat tube in order to hold open atthat location a free supply cross-section 92 of the supply of thefluxing agent to the edge regions of the parting wall 24.

According to FIGS. 5 and 6, generally the surrounding free edge of thedeflecting bowl is bent to the outside thereby forming the opening 90 inthe form of a tulip receiving the free end of the flat tube in such away that the free front side 94 of this free edge extends in theextension direction of the flat tubes 2.

What is claimed is:
 1. A flat tube heat exchanger comprising: a plurality of flat tubes, each said tube having a top end and a bottom end, each said tube divided into a plurality of fluid ducts by a plurality of separating webs, each said tube configured to provide more than two flows; a deflecting bottom disposed near the bottom end of said tubes and including a plurality of deflecting bowls individually assigned to each said tube and deep-drawn from aluminum or an aluminum alloy, the bowls being connected to one another only via their connection to said respectively assigned flat tubes; and a parting wall arranged to sealingly cooperate with the end of a selected separating web formed by a cut out duct of said flat tube which is not used as a guiding duct for a flow and is between adjacent ducts of flows communicating not directly in the bottom end, the parting wall being a local wall design of the deflecting bowl.
 2. A flat tube heat exchanger according to claim 1, wherein the local wall design cooperates only with the selected parting wall of adjacent ducts of said respective flat tube.
 3. A flat tube heat exchanger according to claim 1, wherein the parting wall sealingly engages the insertion member.
 4. A flat tube heat exchanger according to claim 1, wherein the parting wall is formed by locally squeezing longitudinal wall sections of the deflecting bowl from both sides.
 5. A flat tube heat exchanger according to claim 1, wherein the deflecting bowl further comprises a pair of stop bases adapted to engage a front and a rear face of said respective flat tube.
 6. A flat tube heat exchanger according to claim 1, wherein the deflecting bowl has an inner face toward said tubes including a supply flute near the parting wall adapted to permit the supply of a fluxing agent for a braze to the parting wall.
 7. A flat tube heat exchanger according to claim 1, wherein a surrounding free edge of the deflecting bowl is bent to the outside forming an opening in the form of a tulip for receiving the bottom end of said flat tube and extends with a front side into the extension direction of said flat tubes.
 8. A process for manufacturing a flat tube heat exchanger comprising: providing a plurality of flat tubes and a plurality of separate deflecting bowls; forming a parting wall by locally squeezing longitudinal wall sections of the deflecting bowl; mechanically pre-assembling a plurality of structural parts from said deflecting bowls with said flat tubes; mechanically pre-assembling the flat tube heat exchanger from said structural parts; and fastening together the flat tube heat exchanger.
 9. The process of claim 8, wherein providing the plurality of deflecting bowls comprises: providing a plurality of sheet metal blanks; and deep-drawing said sheet metal blanks into said deflecting bowls, each of said bowls having a longitudinal section and a bowl bottom section.
 10. The process of claim 9, wherein said deflecting bowls are drawn from a material selected from the group consisting of aluminum and an aluminum alloy.
 11. The process of claim 8, wherein said fastening comprises soldering together the flat tube heat exchanger.
 12. The process of claim 8, wherein said fastening comprises brazing together the flat tube heat exchanger.
 13. The process of claim 8, wherein the mechanical pre-assembly of the plurality of structural parts comprises: providing a one of the flat tubes having a pair of flat sides; providing a one of the separate deflecting bowls having a bowl bottom section and a longitudinal section rising substantially at right angles to the bowl bottom section; and overgripping the pair of flat sides of the one of the flat tubes with the longitudinal section of the one of the separate deflecting bowls to form a one of the structural parts.
 14. A flat tube heat exchanger comprising: a plurality of flat tubes, each said tube having an upper and a lower end, each said tube including a plurality of reinforcing webs forming at least three longitudinal flow paths; each said tube further comprises an insertion member inset into a cut out longitudinal flow path that is not otherwise used as a longitudinal flow path; and a plurality of separately formed deflecting bowls adapted to sealingly engage the lower end of each said tube, each said deflecting bowl including an intergally formed parting wall extending longitudinally upwardly and preventing fluid communication between at least one pair of adjacent, cross-current longitudinal flow paths, wherein the parting wall sealingly engages the insertion member.
 15. A motor vehicle comprising an evaporator including the flat tube heat exchanger of claim
 14. 